Long Time Autopay User and It (and the employees) Failed Me Today!

Okay, I have used the Autopay system for my GoPhone for a while now. I have made sure that the credit was in the account each time. If for whatever reason, money was tighter than usual, then I cancelled it. This time, my phone renews again in three days. I added the $30 (I already had $10 in there) to the account and went to get the Autopay set up. It wouldn't allow it. Each time it wanted me to add MORE money to the account as I did this online. So I called the customer service line. The customer service representative that I spoke to said that this go around, I would have to just leave the $40 credit in there and it would be used when the phone needed to renew in January, meaning I would have to pay an additional $45 plus tax in order to have my phone work. So I asked her why that is when it clearly stated that I had until the 12th to set up Autopay and I had the money in in plenty of time. She said that that didn't matter, that I would still have to pay again with the card. I am a single parent. I have three kids, two of which have serious health problems. I don't HAVE an addtional $45. I shouldn't have to either when the money is available and ready to go right there in my account. I'm frustrated because I've used Autopay time and time again and using the credit was not an issue. Finally, I told her I needed to speak to a supervisor. Each time she would say that she "spoke to her supervisor" but wouldn't actually let me talk to them myself. After three requests that I, personally, speak to the supervisor, I was put on hold for a while (the supervisor was busy, which is totally understandable and also what I told the representative was fine and I would WAIT for them to become available) the supervisor came on and didn't seem to want to listen to my issues either. She was kind enough to give me a $5 credit so that the plan can renew. Which begs the question... if it was THAT EASY to use the credit for the plan to renew THIS month, why didn't they just allow the dang Autopay. But what really annoyed me was that the supervisor used a voice we all know and love when she said, "There now that I've resolved your issues, thanks again, bye!" in a tone that I can only describe as "I have no desire to speak to you anymore and don't give a crap that you are a customer." Yes, it's a GoPhone. One that I've had for over a year now. I've busted my butt as a single parent to keep this plan. I've had to drop down to the $30 plan when times were tough. I had a $60 plan when they weren't. But after one phone call, I have almost no desire to be an AT&T customer again. I am the least likely person on the planet to get frustrated with someone when they are simply doing their job. But this? This was unacceptable. I am not one to ask for freebies. I am not one to accept a free meal or a coupon. But honestly, this company has to give me a darn good reason to stick around after what just happened. I was understandably frustrated. I had just spent the last of my money to ensure I had a phone and while I did get the $5 credit, what I wanted is for them to listen to me, which they didn't. So, tell me, what do I do? Because I have never been so frustrated in my life, got hung up on by a supervisor with a particularly catty "bye" and am frankly shocked that your customer service representatives are trained in such a way that they can't actually help anyone to the point that a supervisor gets annoyed that they even have to speak to someone like me. I need convincing and this needs to be fixed AT&T. Because come January, if it isn't, I will be looking for a new company.